BR112014017695B1 - PROCESS FOR PRELIMINARY CAST IRON TREATMENT - Google Patents

Abstract

summary "process for preliminary treatment of cast iron". A process for the preliminary treatment of cast iron is proposed in which, in the desiliconization, dephosphorization and decarburization processes, a heat source for scrap melting is obtained while the amount of flux used is minimized and the phosphorus concentration is effectively reduced. Iron yield is increased. a process for the preliminary treatment of cast iron in which the desiliconization and dephosphorization treatments of cast iron are performed using a converter type container, wherein: the cast iron is first loaded into the converter type container and is carried out the desiliconization treatment; then an intermediate processing with the slag is performed; thereafter a lime based flux is added to the vessel and oxygen is inflated and the cast iron is subjected to dephosphorization treatment; The new untreated cast iron is then loaded into the container and the desiliconization treatment mentioned above is performed and the above processes are repeatedly carried out continuously using the same container.

Description

(54) Title: PROCESS FOR PRELIMINARY CAST IRON TREATMENT (51) Int.CI .: C21C 1/02; C21C 1/04; C21C 5/28; C21C 5/36 (30) Unionist Priority: 16/01/2013 JP 2013-005194, 19/01/2012 JP 2012-008811 (73) Holder (s): JFE STEEL CORPORATION (72) Inventor (s): RYO KAWABATA ; YOZO IWAKI; SHIZUHIKO IKENO; KOCHIRO EJIMA; TAKESHI ISHII; MASANORI NISHIKORI; HIRONORI FUKUSHIMA; NAOKI KIKUCHI; NORIHIKO SUZUKI; KOTARO TANAKA; KAZUHITO YAMAMOTO; NAOTAKA SASAKI; YASUSHI OGASAWARA; FUTOSHI OGASAWARA; YUICHI UCHIDA; MASAOMI SENOO; MANABU TANO

1/53

PROCESS FOR PRELIMINARY CAST IRON TREATMENT.

TECHNICAL FIELD [001] This invention relates to a process for the preliminary treatment of cast iron and more particularly to a process for conducting both desilicate and dephosphorization in a (the same) converter type container.

BACKGROUND TECHNIQUE [002] In general, cast iron is subjected to a preliminary treatment to preliminarily remove silicon and phosphorus from cast iron prior to decarburization refining in a converter. The preliminary treatment of the cast iron is carried out with the purpose of decreasing an amount of used refining flux, improving the purity of the molten steel, improving a manganese yield by preventing peroxidation in an operation with a converter, decreasing an amount of slag for refining etc. and several methods that include treatment in the decarburization stage are proposed for this.

[003] Slag for refining is generated in the preliminary treatment of cast iron. When refining slag is used for various applications, it is necessary that fluorine and the like are not eluted depending on the application. For this purpose, a process for conducting a preliminary treatment of cast iron that does not use fluorite (CaF ₂ ) as a source of fluoride has been reviewed so far to improve the efficiency of dephosphorization. Recently, the volume of greenhouse gas emissions in the steel industry is also being asked to reduce. Under this connection, a refining method is revised in which the rate of use of cast iron from a blast furnace that requires great energy to reduce iron oxide is decreased while an rate of use of iron source is increased

Petition 870180032588, of 04/20/2018, p. 5/70

2/53 cold such as iron scrap or similar. Under such a situation, the recent method for preliminary treatment of cast iron tends to increase the rate of use of the cold iron source while improving the refining method.

[004] As one of the preliminary cast iron treatments that lead to desilication or dephosphorization of the cast iron, there is a process in which the silicon or phosphorus in the cast iron is removed in a slag by adding a refining agent (solvent of flux) such as quicklime or similar to cast iron while adding a gaseous oxygen or a solid oxygen source such as iron oxide or the like. As a container for the treatment of cast iron, a transport container such as a carburettor, blast furnace vat or the like, a converter-type vessel (refining furnace) etc. are used. To use a large amount of scrap, it is advantageous to use a converter type container that has a large capacity.

[005] In Patent Document 1 a method of refining cast iron is described which leads to desilication and dephosphorization with a converter in which the removal of the intermediate slag is carried out after desilication in the converter and subsequently dephosphorization is carried out. This method proposes a process in which refosphorization after desilication is suppressed by controlling the composition of the slag to facilitate subsequent dephosphorization. [006] Patent Document 2 describes a process for the preliminary treatment of cast iron in which desilication is carried out with a converter-type reactor and the desilicated cast iron after dumping and slag removal is returned to the reactor again. to drive dephosphorization. This method for the preliminary treatment of cast iron is a process of conducting dephosphorization effectively by adjusting silicon concentration,

Petition 870180032588, of 04/20/2018, p. 6/70

3/53 basicity of slag and concentration of iron oxide in cast iron after desilication without using fluorite and a process of dissolving scrap in desilication and / or dephosphorization. [007] Patent Document 3 describes a process for preliminary treatment that continuously leads to desilication and dephosphorization of cast iron with a converter-type container in which 40 ~ 60% by weight of a slag generated after dephosphorization of a previous charge is retained in the container and used for desilication and dephosphorization to reduce the amount of slag generated.

PREVIOUS TECHNICAL DOCUMENTS

PATENT DOCUMENTS [008] Patent Document 1: JP-A-2001-271113 [009] Patent Document 2: JP-A-2002-129221 [0010] Patent Document 3: JP-A-2002-256325

SUMMARY OF THE INVENTION

TASK TO BE SOLVED BY THE INVENTION [0011] In the method described in Patent Document 1, it is attempted to suppress the phosphorization after desilication by controlling the slag composition so that the slag basicity is approximately 0.9 ~ 1.1 and T. Fe is around 15 ~ 20% by weight after desilication. In this described technique, however, there is a problem that the phosphorization is caused when T. Fe is not more than 15% by mass at a slag basicity of 0.9 ~ 1.1 and therefore the phosphorus concentration in compacted cast iron it gets bigger.

[0012] The method described in Patent Document 2 is advantageous for decreasing the concentration of cast iron phosphorus because the act of dumping the cast iron from the converter type container and removing the slag are carried out after desilication and the funPetition iron 870180032588 , of 04/20/2018, p. 7/70

4/53 The desiccated salt is returned to the container to conduct dephosphorization. However, the act of dumping and the load of cast iron are repeated, so that there is a problem that productivity is considerably deteriorated when these operations are carried out using a (the same) converter-type container. On the other hand, two converter type containers can be used, but there is a problem that the cost of installation is high and the heat loss due to the thermal dissipation from the container is increased. In addition, there is a problem that as it is necessary to add a greater amount of solvent to the flux and in desilicate and dephosphorization, the increase in refining cost is caused and the heat loss due to the absorption of heat by the flux solvent is increased.

[0013] In the method disclosed in Patent Document 2, iron oxide such as iron ore or the like is loaded in dephosphorization to promote slag formation or improve the efficiency of dephosphorization. Therefore, there is a problem that the heat absorption associated with the oxidation reaction of iron oxide oxidizes or the heat loss due to the act of pouring intermediate is large and, therefore, the amount of heat sufficient to dissolve a greater amount of scoria. scrap cannot be guaranteed. In this process, as the basicity is relatively high, the proportion of the solid phase in the slag becomes higher even at the end of the dephosphorization and the fluidity is low and therefore droplets of cast iron are incorporated into the slag and removed from the container and solidified without separate. Consequently, there is a problem that the increased loss of base metal is caused. That is, a part of the base metal can be recovered as an ion source by magnetic separation after spraying the slag, however the iron particles incorporated into the slag cannot be recovered and, therefore, most

Petition 870180032588, of 04/20/2018, p. 8/70

5/53 of it is diverted to civil and similar applications together with the slag and the loss of the base metal is great.

[0014] Patent Document 3 proposes a pretreatment method in which desilicate and dephosphorization are carried out continuously in a converter-type container, while only 40 ~ 60% by weight of the slag is discharged after dephosphorization and the rest is used in the desilication and dephosphorization of the next load to decrease the amount of solvent for the used flux and the amount of slag generation, so that the decrease in heat loss is expected. However, Patent Document 3 does not present a slag composition and preferably the treatment temperature range for desilication and dephosphorization. As dephosphorization is carried out while maintaining a large amount of desilicate slag in the container, it is necessary to use a large amount of a solvent for the lime based flux to adjust the basicity of the slag in the production of low phosphorus cast iron. . Consequently, desilicate slag is not caused, whereas the amount of dephosphorized slag is increased in the vessel to decrease the efficiency of the reaction and the amount of dephosphorized slag discharged is inversely increased, so there is a problem that is caused by the loss of base metal incorporated into dephosphorized slag.

[0015] A main objective of the invention is to propose a process to effectively conduct the desilicate and dephosphorization of cast iron in a small amount of a solvent for the used flux. Another objective of the invention is to propose a process for the preliminary treatment of cast iron that is capable of suppressing the cost of producing low phosphorus cast iron, increasing the amount of scrap used and also reducing the loss of

Petition 870180032588, of 04/20/2018, p. 9/70

6/53 base metal incorporated into the slag.

TASK SOLUTION [0016] The inventors have carried out several studies in a process in which the concentration of phosphorus can be effectively decreased even when the amount of solvent for the used flux is suppressed in the process of desilication, dephosphorization and decarburization and the heat source to dissolve the scrap it can be guaranteed sufficiently to improve the yield of the iron. Consequently, it has been found that the above objectives can be achieved by an appropriate adjustment of the amount of slag retained in the converter and transported to the subsequent step and treatment conditions such as slag composition, temperature and the like in the preliminary treatment leading to desilication and dephosphorization of cast iron and, as a result, the method of preliminary treatment of cast iron according to the invention can be carried out.

[0017] That is, the invention is a process for the preliminary treatment of cast iron by conducting the desilication and dephosphorization of the cast iron with a converter-type container in which the cast iron poured from a blast furnace is first loaded into the vessel. converter type to conduct desilicate and then cast iron and a part of the slag after desilicate and then the cast iron and a part of the slag after desilicate are kept in the container to drive the removal of the intermediate slag and subsequently a solvent for the flux lime-based is added to the cast iron and the slag kept in the container after desilication while oxygen is being blown to conduct dephosphorization of the cast iron, characterized by the fact that no less than 30% by weight of a slag that has a slag basicity of not less than 1.2 after dephosphorization is maintained in the converter-type container and then at least iron

Petition 870180032588, of 04/20/2018, p. 10/70

7/53 untreated melt is loaded into the container containing the slag after dephosphorization to conduct desilicate and the silicon concentration of the molten iron at the end of the desilicate is obtained to no more than 0.2% by mass and a basicity of slag after desilication is obtained up to not less than 0.5 but not more than 1.5 and the temperature of the cast iron is obtained up to not less than 1240 ° C but not higher than 1400 ° C and thereafter an intermediate removal of discharge slag of not less than 40% by mass of the slag is carried out after desilication from the container and subsequently dephosphorization is carried out in the same container.

[0018] In the invention, the following means of solution are preferable:

(1) the slag basicity after dephosphorization is not higher than 3.0;

(2) the slag after dephosphorization is retained in the container to not less than 60% by mass of an amount generated by dephosphorization;

(3) a slag basicity during desilication is not less than 0.8, but not greater than 1.5;

(4) the slag after desilication has a slag basicity of not less than 0.8, but not more than 1.5 and T. Fe of not less than 5% by weight, but not more than 25% by mass;

(5) the cold iron source is loaded during desilication;

(6) desilication is carried out by loading the cold iron source into the converter-type container in addition to the cast iron poured out of the blast furnace and by inflating oxygen to bring the temperature of the molten iron at the end of the desilication to not less than 1260 ° C, but not greater than 1350 ° C;

Petition 870180032588, of 04/20/2018, p. 11/70

8/53 (7) an amount of a cold iron source that satisfies the following equation is loaded for desilication by a total amount of cast iron and the cold iron source loaded in the converter-type container:

Y = (3 + 34.5 [% Si] + 0.21Ti) (1000 - Xs) / 1000 where Y is 230 ~ 270.

[0019] [% Si] is the concentration of silicon in the charged cast iron (% by mass), [0020] Ti is the temperature of the loaded cast iron (° C) and [0021] Xs is a basic unit of a source of cold iron (kg / t);

(8) the concentration of silicon in the cast iron at the end of desilication is not more than 0.1% by mass;

(9) dephosphorization is conducted by loading or adding 100 ~ 250 kg / t of the cold iron source and 2 ~ 10 kg / t of silicon as an oxide by total weight of cast iron and the cold iron source for the container converter type;

(10) dephosphorization is carried out keeping 4 ~ 20 kg / t of slag after desilication by the total weight of the cold iron and cast iron in the converter-type container after the intermediate removal of the slag, by adding a solvent for the lime based flux and oxygen insufflation in order to make a slag basicity after dephosphorization of not less than 1.2 but not more than 3.0 and the temperature of the cast iron after the end of dephosphorization not less than 1280 ° C but higher than 1360 ° C;

(11) dephosphorization is carried out by applying a jet of refining agent that contains at least one ingredient of powdered lime, calcium carbonate and iron oxide to a molten metal through an insufflation lance at the top.

EFFECT OF THE INVENTION

Petition 870180032588, of 04/20/2018, p. 12/70

9/53 [0022] According to the method for the preliminary treatment of cast iron according to the invention having the aforementioned construction, a lime content in the slag after dephosphorization can be used as a source of lime in the desilication of the next charge and can suppress the phosphorization in the desilication, so that it is possible to decrease the amount of the solvent for the lime based flux during the whole process of preliminary treatment of the cast iron.

[0023] According to the invention, intermediate slag removal and subsequent dephosphorization are carried out in the same container after desilication, so that an amount corresponding to the heat dissipation due to displacement of the refining container can be a source of heat to dissolve the cold iron source, while the high temperature slag generated by the pre-charge after dephosphorization can be used as a solvent for the flux and therefore an absorbed heat content can be used as a heat to dissolve the source of cold iron compared to the case of adding solvent to the flux at room temperature. As a result, it may be attempted not only to increase the amount of the cold iron source (scrap) used, but also to reduce the loss of base metal.

[0024] According to the invention, the slag generated in the desilicate which has a low basicity is discharged from the container between the desilicate and the dephosphorization, so that the amount of solvent for the lime-based flux can be reduced in the necessary dephosphorization. to be carried out at a relatively high basicity ((% by mass CaO /% by mass SiO2) = 1.2 ~ 3.0) and the cost of producing cast iron can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS [0025] FIG. 1 is a schematic view of a container of the type

Petition 870180032588, of 04/20/2018, p. 13/70

10/53 converter (refining oven) used in the method for preliminary treatment of cast iron according to the invention.

[0026] FIG. 2 is a schematic view illustrating the method for the preliminary treatment of cast iron according to the invention following the process.

[0027] FIG. 3 is a graph showing a relationship between slag basicity, proportion of slag removal and slag viscosity.

[0028] FIG. 4 is a graph showing a relationship between a degree of progression in inflation and a calculated basicity in a container.

MODALITIES FOR CARRYING OUT THE INVENTION [0029] The invention will be described with reference to the following drawings.

[0030] In the process for the preliminary treatment of cast iron according to the invention, a furnace 1 for refining of the inflatable converter type at the top and bottom as shown in FIG. 1 is used as an example of the converter type container. In the furnace 1 for refining, an insufflation is carried out at the top by insufflation of gaseous oxygen 12 by a tip of an insufflation lance 2 lifting at the top towards the cast iron 9. As gaseous oxygen 12 is used pure industrial oxygen. In addition, insufflation at the bottom is carried out by nozzles 3 for insufflation at the bottom arranged at the bottom of oven 1 for refining. As a gas 13 for bottom insufflation, a gas containing gaseous oxygen or an inert gas such as gaseous air, gaseous nitrogen or the like is common, but a gas that has a function to reinforce the agitation of the cast iron 9 and to promote the dissolution of a cold iron source by insufflation in the cast iron or also a gas that has the function of insufflating a solvent for the flux in the cast iron together with a carPetition gas 870180032588, of 04/20/2018, p. 14/70

11/53 reador. In addition, numeral 4 in the figure is a withdrawal orifice for pouring cast iron 9 after refining.

[0031] In the invention, two or more converter type refining furnaces 1 are used in refining cast iron, wherein at least one of the converter type refining furnaces 1 is used in the preliminary treatment of the cast iron according to the invention and a remaining furnace is used in refining by decarburizing the cast iron subject to the preliminary treatment of the cast iron by applying a method of the invention. For example, it is preferable that the preliminary treatment is carried out in the converter type refining furnace 1 for the preliminary treatment of the cast iron and the cast iron after the preliminary treatment is moved in the converter type refining furnace for the decarburization refining to conduct decarburization.

[0032] The process for preliminary treatment of the cast iron according to the invention using the converter type refining furnace 1 is carried out in the order of (A) loading the cast iron, (B) desilicating, (C) intermediate removal of the slag, (D) dephosphorization and (E) pouring of the cast iron as shown in a flow chart of FIG. 2. Especially, it is possible to effectively conduct the preliminary treatment of the cast iron by repeating these steps in the same oven.

[0033] (1) First, a loading step for the cast iron (A) will be explained.

[0034] In step (A), a new cast iron 9 is loaded from a shell 14 for loading while retaining the slag 17 generated after dephosphorization by preliminary treatment of the pre-loaded cast iron (hereinafter simply called slag after dephosphorization) ) in the converter type refining furnace 1 or in the cold iron source 11 such as scrap iron or the like before loading the cast iron and then the casting iron 9 is loaded. CoPetition 870180032588, of 04/20/2018, p. 15/70

12/53 mo the previously loaded cold iron source 11 may be composed mainly of iron such as direct reduced iron, cold pig iron and the like in addition to the iron scrap defined in Japan's Uniform standards of Ferrous Scraps ferrous raw materials association. [0035] Slag 17 after the previous dephosphorization retained in the refining furnace 1 for the next refining is used for the purpose of adjusting the basicity of the slag in the subsequent desilicate. The basicity of the slag after dephosphorization (% by mass of CaO /% by mass of SiO2) (hereinafter referred to simply as basicity) is obtained up to not less than 1.2, preferably not less than 1.4, For this reason , when the basicity of the slag 17 after dephosphorization at the end of the preceding dephosphorization is less than 1.2, even if such slag is retained, the basicity adjustment in the desilicate is insufficient and it is necessary to add a large amount of solvent to the flux based on lime. In addition, the upper limit of the slag basicity after dephosphorization is not particularly limited, but the slag basicity in the usual dephosphorization of cast iron is not more than approximately 3.0, so it is not necessary to increase the basicity in a way exceeding the above value.

[0036] It is necessary that the amount of slag 17 after the previous dephosphorization retained in the oven should not be less than 30% by weight of the amount of slag generated in the previous dephosphorization of cast iron, preferably not less than 60% by weight for efficiently conduct the basicity adjustment. In the invention, when the total amount of slag retained in the kiln after pouring cast iron during dephosphorization is used in the new desilication of the cast iron, the adjustment of the basicity becomes even more effective in the desilication. In addition, when such a procedure is conducted continuously, the slag discharged

Petition 870180032588, of 04/20/2018, p. 16/70

13/53 by the preliminary treatment of cast iron it becomes homogeneous because it is comprised only of a slag after desilication and a slag after dephosphorization which has a high basicity not incorporated in it, so that no problem such as swelling is caused slag due to hydration, alkali elution or similar. Therefore, the method of the invention is very effective in attempting to use the slag.

[0037] The slag after dephosphorization has a relatively high basicity and a relatively low temperature (not higher than approximately 1350 ° C), so that the fluidity is low. Therefore, even when the cold iron source is loaded onto the slag after dephosphorization, no dissolution delay is caused due to the adhesion of the cold iron source to the slag, so that there is no need for an ineffective operation in thermal balance and mass balance such as adding a large amount of cooling material for solidification as in a case where the so-called decarburized slag is retained in the oven. In addition, the slag after dephosphorization is rich in the solid phase and has low fluidity because of the above properties, so that a large amount of fine metallic iron is contained in its structures. Therefore, the slag contains no less than approximately 10% by weight of metallic iron even after spraying and magnetic separation. Although the slag is discharged out of the system in the conventional technique, the slag after dephosphorization can be transported to the next load according to the invention, so that there is also an effect that most of the metallic iron in the slag after the dephosphorization is recovered in the cast iron to reduce iron loss.

[0038] In the slag at the end of desilication (here after slag after desilication), fluidity is relatively high,

Petition 870180032588, of 04/20/2018, p. 17/70

14/53 so that the metallic iron content in the slag is easily made higher. Therefore, there is a small amount of metallic iron retained in the slag without being recovered after spraying and magnetic separation of the slag. In this way, the process of the invention can reduce the loss of fero to the slag throughout the preliminary treatment of the cast iron.

[0039] (2) Then, a desilication step (B) presented in FIG. 2 (B).

[0040] Step (B) is a step of conducting desilication by placing the converter type refining oven 1 vertically and supplying gaseous oxygen 12 to the cast iron 9 through a lance 2 of the type that inflates from the top. In this desilication, a silicon source 15 housed in a tank 5 and a solvent for the lime-based flux 16 housed in a tank 7 for the refining furnace 1 of the converter type are loaded through an inclined tube 6 of an inclined tube. 8, respectively, while the carbonaceous material or the silicon source as the heat source, iron oxide as the oxygen source or the like is also charged in a similar manner. As the oxygen source for desilication, it is preferable to use only gaseous oxygen 12 without using iron oxide, which has great heat absorption from the point of view of dissolving a large amount of a cold iron source 11.

[0041] In desilication, the silicon contained in the molten iron 9 or the silicon included in the silicon source 15 and the cold iron source 11 and which migrates to the molten iron by dissolution is desilicated by reaction with the oxygen source (Si + O2 SiO2), so that it serves to improve the efficiency of the reaction in the subsequent dephosphorization. During desilication oxidation heat is generated and the temperature of the cast iron is raised by this oxidation heat to promote the dissolution of the cold iron source 11 in the cast iron.

Petition 870180032588, of 04/20/2018, p. 18/70

15/53 [0042] The composition of the slag in the desilication stage is determined by considering the amount of slag 17 after the previous dephosphorization retained previously in the oven and an estimated value of its composition and an amount of silicon dioxide generated in the above reaction .

[0043] Namely, it is preferable to adjust the basicity of the slag during desilication to not less than 0.8, but not more than 1.5. For this reason, when the slag basicity in desilication is less than 0.8, the phenomenon of phosphorization is observed due to the decrease of the dephosphorization capacity in slag 17 after dephosphorization depending on the mass% of Si of the cast iron as shown in FIG. 4. For example, FIG. 4 shows three patterns that the Si in the cast iron is 0.45% by mass, 0.46% by mass and 0.55% by mass. The concentration of phosphorus before and after desilication in each standard is dephosphorized from 0.121% by weight to 0.100% by weight in the case of Si in cast iron from 0.45% by weight and from 0.122% by weight to 0.105% by weight. mass in the case of Si in the cast iron is 0.46% by mass as observed by Examples 10 ~ 12 in Table 3. However, when the Si in the cast iron is 0.55% by mass, the concentration of phosphorus is obtained from 0.120% by weight to 0.145% by weight. This is due to the fact that since the basicity in desilication is less than 0.8, the phosphorus concentration after desilication is increased to cause refosphorization. On the other hand, when the slag basicity exceeds 1.5, the proportion of the solid phase rises due to the increase of CaO without slag and the slag fluidity 17 after dephosphorization is deteriorated and a case in which the slag cannot be removed. The preferred upper limit is approximately 1.2.

[0044] In addition, the basicity calculated in the oven (C / S) during

Petition 870180032588, of 04/20/2018, p. 19/70

16/53 desilication shown in FIG. 4 is a calculated value based on equation (1) below. Equation (1) determines the basicity (CaO / SiO2) of a numerical value obtained by adding an amount of CaO contained in the dephosphorized slag retained in the oven with an amount of CaO generated in the respective charge up to a time T [s] and a numerical value obtained by adding an amount of SiO2 in the residual slag dephosphorized with an amount of SiO2 generated in the respective charge up to a time T [s]. In addition, the amount of CaO generated in the respective load is a numerical value obtained by calculating and adding an amount of CaO (= CaO content in the auxiliary material x residence time in the oven x dissolution rate) for each loaded auxiliary material.

[0045] In addition, the amount of SiO2 is a numerical value obtained by adding the oxygen feed rate x (molecular weight of SiO2) / (atomic weight of Si) / (theoretical amount of Si burned by oxygen of 1 Nm ³ ) x efficiency of desiccation oxygen up to a time T.

c / s _? laughs = _ ₍₁₎

5iO2, LfeJ + 502 _s [£ g]

CaOJJÍg] = ^ [Ag] x CaO%, [%] / 100 = Xc _fl o% ₃ [%] x?; Wx! Kg} i 100

SiO2 _A [Ag] = Ws _A x SiO2% .J%] / 100

A'02 / Agl = £>C> ₂ [/ Vm ³ / λ] x 2.14 / 0.8 ^ 3 / ^ - /] *? _ísi [-] x Λψ]

Where [0046] C / St [-]: basicity calculated at a time T [s] [0047] CaOA [kg]: amount of CaO in the slag retained in the oven [0048] CaOB [kg]: amount of CaO generated in the respective charge up to time T [s] [0049] SiO2A [kg]: amount of SiO2 in the slag retained in the kiln [0050] SiO2B [kg]: amount of SiO2 generated in the respective charge up to time T [s]

Petition 870180032588, of 04/20/2018, p. 20/70

17/53 [0051] WsA [kg]: amount of slag retained in the oven [0052] CaO% A [%]: amount of CaO retained in the oven (% by mass) [0053] SíO2% to [%]: content of SiO2 in the slag retained in the oven (% by mass) [0054] CaO% to [%]: CaO content in the auxiliary material (% by mass) [0055] Ta [s]: retention time of auxiliary material in an oven [ 0056] Va [s / kg]: dissolution rate of auxiliary material in an oven [0057] VO2 [Nm ³ / s]: oxygen supply rate in insufflation [0058] nSi [-]: oxygen efficiency for desilication on inflation [0059] Xs [ton / load]: total amount of cast iron and amount of scrap.

[0060] The% CaOa above is obtained by calculating calcined lime, calcium carbonate or the content of CaO in the recycled slag. In addition, cast iron or cast steel in the furnace is subjected to batch-type refining in the refining furnace such as a converter-type or similar refining furnace, where the refining of a unit is called a charge.

[0061] Next, the basicity of the slag at the end of the desilication is adjusted to not less than 0.5 but not greater than 1.5. When the basicity of the slag at this stage (slag after desilication) is less than 0.5, the phosphorus is recovered from the slag 17 after the previous dephosphorization retained in the furnace to cause approximately an increase in the concentration of phosphorus in the cast iron and the charge dephosphorization in the subsequent stage becomes large, which is ineffective. Therefore, the basicity of the slag after desilication at the end of desilication is not less than 0.5, preferably not less than 0.8. In addition, when the slag basicity in this stage exceeds 1.5, the slag fluidity is diPetition 870180032588, from 04/20/2018, p. 21/70

18/53 reduced, so that there is a problem that the amount of slag removal in the subsequent intermediate slag removal is less or the slag removal control is difficult, which is not efficient even in reducing the solvent to the base flux of lime. Therefore, the basicity of the slag after desilication is not more than 1.5, preferably not more than 1.2. In basicity adjustment, the solvent for the lime based flux such as calcined lime, limestone, dolomite or similar and the steel that produces slag selected from decarburized slag, dephosphorized slag and the slag shell are used as a solvent for the flux .

[0062] The temperature of the cast iron at the end of the desilication is adjusted to not less than 1240 ° C but not less than 1400 ° C, preferably not less than 1260 ° C but not less than 1350 ° C. When it exceeds 1400 ° C, dephosphorization is caused by the dephosphorized slag retained in the furnace to cause approximately an increase in the concentration of phosphorus in the cast iron, so that not only does the dephosphorization charge in the subsequent step become large and it is ineffective but it is also It is necessary to increase the concentration of magnesia in the slag to avoid damage to the carbon bricks coated with magnesia, which causes approximately the cost increase. Although it is less than 1240 ° C, slag fluidity is decreased and not only is there a problem that the amount of slag removal in the subsequent intermediate slag removal is less and controlling the amount of slag removal is difficult, but the rate of dissolution of scrap is also reduced.

[0063] In addition, it is necessary to control the temperature of the cast iron at this stage to effectively conduct dephosphorization in the subsequent dephosphorization stage. For example, when the temperature of the cast iron at the end of the desilication is obtained no higher than 1350 ° C, the amount of the cooling material can be obtained. Petition 870180032588, of 04/20/2018, p. 22/70

19/53 such as iron ore or similar to be added to adjust the temperature at dephosphorization can be decreased dramatically. In addition, when desilicate and dephosphorization are carried out continuously in the same furnace, it may be a case that loading or scrapping is difficult before dephosphorization in view of the operating time. In addition, the cold iron source capable of being loaded from the top of the furnace during treatment is an expensive granulated source or a base metal generated in iron mills and is quantitatively restricted, so that it is difficult to use regularly in a large amount. In fact, the cold iron source may not be loaded from the top of the oven due to the restriction on the type of auxiliary material capable of being used by the device for loading above the oven. Until now, the cooling material used in the dephosphorization step has been limited to iron oxide such as iron ore or the like, so it is common that the cheap cold iron source such as scrap and the like cannot be used sufficiently.

[0064] In general, it is relatively easy to increase the amount of cheap scrap used in the desilication step, so that the temperature of the cast iron after desilication can be raised to no higher than 1350 ° C. In this way, the amount of iron oxide used in the dephosphorization stage can be significantly decreased. As a result, a large amount of heat absorption due to the iron oxide decomposition reaction can be decreased and the amount of heat from it can be associated with the dissolution of a cold iron source in desilication. In addition, if the temperature is lowered after desilication, there is a fear that the scrap will be left undissolved, however the scrap left is kept in the oven together with the cast iron and the dissolution can be promoted to the subsequent dephosphorization stage.

Petition 870180032588, of 04/20/2018, p. 23/70

20/53

That is, when the cold iron source is dissolved until the end of dephosphorization, no problem is caused in the operation.

[0065] When the temperature of the cast iron after desilication can be used as a value measured by a thermocouple or a value estimated by the thermal balance. For example, the thermal equilibrium estimate can be conducted according to equation (2) below, but is not necessarily limited to it. Because of this, the coefficient is adjusted depending on the respective condition of the apparatus or the operating condition and the variable is added or removed. In addition, if the scrap is left undissolved after desilication, the measured value tends to be slightly higher than the estimated value but is in the error range and has no objection.

T = {0,21Ti Xp-42,9Xs + (4137 + 0,327Ti) Xsi-746,6Xc (575,5 + 0,025Ti) Xore + (3239-0,115Ti) XO2 + 28,2Xf-1638W ^{- (1/3 )} Xt} / (0.21Xp + 0.179Xs + 0.535Xsi + 0.448Xc + 0.151Xore + 0.115Xo2 + 0.241Xf) - (2) [0066] T: temperature of the cast iron after desilication (° C) [0067] Ti: temperature of the loaded cast iron (° C) [0068] Xp: basic unit of cast iron (kg / t) (per 1 ton in total weight of cast iron and one weight of the cold iron source, the same if applies here below) [0069] Xs: basic unit of a cold iron source (kg / t) [0070] Xsí: basic unit for forming an oxide silicon (kg / t) (total included in cast iron, in cold iron source and additive) [0071] Xc: basic unit of carbon in the additive (kg / t) [0072] Xore: basic unit of iron oxide (kg / t) [0073] X02: basic unit of gaseous oxygen (Nm ³ / t) [0074] Xf: basic solvent unit for the flux (kg / t) [0075] W: volume of cast iron in the converter (t)

Petition 870180032588, of 04/20/2018, p. 24/70

21/53 [0076] Xt: the time from the spillage of the previous charge until the end of the desilication (minute) [0077] In this case, the silicon that forms an oxide is a total included in the cast iron, in the cold iron source and in the additive. As the concentration of silicon in the cast iron between them is used a fast analytical value of a sample taken from the cast iron before loading each load. However, an alternative method can be used by performing an operation with another analytical value of ingredients poured from the blast furnace. When the concentration of silicon in various sources of cold iron is used, for example, an analytical value for each batch of a typical sample, however the concentration in cold pig iron is the same as that in cast iron and is often stable. In addition, the silicon concentration in the scrap is varied depending on the source, but is stable at a value of no more than approximately 1/10 of pig iron on average, which can be used as a typical value or can be negligible.

[0078] In the additive there is silicon without oxide as the silicon that forms an oxide (the silicon existing in an oxidizable state). This means iron silicide, metallic silicon, silicon carbide, silicon nitride or other silicide. As the typical additive can be mentioned ferrosilicon, briquette made of powder containing approximately 60% by weight of silicon carbide (hereinafter referred to as silicon carbide briquette) etc.

[0079] As the silicon analysis method of no oxide in the additive, a ferrosilicon analysis method described in JIS G1312 is used, but an estimate can be conducted by using total silicon analysis, acid-soluble silicon analysis, analysis total carbon, total oxygen analysis, total nitrogen analysis, thermal mass analysis, carbon analysis using the combustion method adjusted by temperature hysteresis, analysis of other elements includedPetition 870180032588, from 04/20/2018, p. 25/70

22/53 dos, analysis of compounds by means of X-ray diffractometry and the like in combination.

[0080] In addition, the additive contains carbon. As carbons are used not only carbonaceous material such as coke, amorphous graphite or the like, but also carbon in a carbide such as silicon carbide mentioned above or the like. Auxiliary materials such as quicklime, light calcined dolomite, magnesia binder and the like are used as fluxing solvents. In addition, slag such as dephosphorized slag, decarburized slag, shell slag and the like can be used as a source of calcium oxide or as a source of magnesium oxide. As an example of the low-cost auxiliary material, calcium or magnesium carboxide, hydroxide or the like can be used. However, as they have high heat absorption, if they are used in a large amount, it is desirable to modify equation (2) above discriminating against another solvent for the flux.

[0081] To reach the temperature of the cast iron after desilication to the range above 1240 ~ 1400 ° C while trying to increase the amount of a cold iron source used and to suppress the cost of refining, the basic unit of the iron source cold Xs (kg / t) by total weight (t) of a cold iron and cast iron source it is preferable that it be obtained within a range of not less than 230, but not greater than 270 as a value of Y calculated from according to equation (3) below. When Y is less than 230, it is necessary that carbonaceous material such as amorphous graphite or the like be added as a heat source to prolong the inflation time or the calcium oxide source is added to adjust the slag basicity to the same time using a large amount of costly heat source such as ferrosilicon or similar and, therefore, the increase in refining cost or decrease in productivity caused undesirablePetition 870180032588, of 04/20/2018, p. 26/70

23/53 mind. Meanwhile, when the value of Y in equation (3) exceeds 270, the cooling material such as iron ore or similar is used to control the temperature, which is unfavorable from the point of view that the amount of the used cold iron is obtained maximum.

[0082] Y = (3 + 34.5 [% Si] + 0.21Ti) (1000-Xs) / 1000 (3) [0083] Y: 230 ~ 270 [0084] [% Si]: silicon concentration in loaded cast iron (% by mass) [0085] Ti: temperature of loaded cast iron (° C) [0086] Xs: basic unit of the cold iron source (kg / t) [0087] In the invention, basic unit of the source of cold cold iron is adjusted as mentioned above, however an appropriate amount of silicon that has a large amount of heat generation can be used as a heat source to dissolve a large amount of the cold iron source over a short period of time. In this case, it is preferable that the total amount of oxide-free silicon added to the load or desilicate is in a range of 2 ~ 10 kg / t, preferably in a range of 4 ~ 8 kg / t by total weight of cast iron and from a cold loaded iron source. In this connection, when silicon is added in an amount that exceeds 10 kg / t, the amount of silicic acid generated in the desilication becomes excessive and even if the desilication is carried out while a total volume of the slag is left in the oven after dephosphorization. from the previous load, it is necessary to add a large amount of calcium oxide source for an additional adjustment of the basicity and therefore the amount of slag in the kiln becomes large, which is not preferable from a refining cost point of view and the like. Meanwhile, when the amount of silicon is less than 2 kg / t, the amount of heat generation by oxidation reaction is small, which is not

Petition 870180032588, of 04/20/2018, p. 27/70

24/53 effective for the dissolution of the cold iron source. In addition, the amount of silicic acid generated is decreased in the desilication stage and when a large amount of dephosphorized slag that has a high basicity is left in the oven, the basicity after desilication becomes high, which is an obstacle in removing subsequent slag and therefore it is undesirably necessary to adjust the basicity by adding a source of unproductive silicate thermally or as a resource. In this connection, the amount of silicon of 4 ~ 8 kg / t is said to be a preferable range to adjust the basicity after desilication or to guarantee the heat source for the dissolution of the cold iron source.

[0088] As the source of silicon to be added ferrosilicon can be used, however it is preferable to use a silicon carbide briquette composed mainly of cheaper silicon carbide or a residue refractory composed mainly of silicon carbide. Furthermore, it is not necessary to use only this source of silicon as a source of heat and the other source of heat such as carbonaceous material or the like can be used within a range that does not decrease productivity. It is desirable for the carbonaceous material to be added by predicting the amount of decarburization in order to make the concentration of carbon in the cast iron at the end of the desilication not less than 3.3% by mass. When it is less than 3.3% by mass, the heat source is lacking in the subsequent dephosphorization and decarburization steps and also the carburizing speed on the surface of the cold iron source such as scrap or similar is slowed down to cause approximately decreasing the dissolution rate.

[0089] In the desilication of the invention, the temperature of the cast iron after desilication is controlled to an appropriate range, while silicon is used as a heat source, so

Petition 870180032588, of 04/20/2018, p. 28/70

25/53 that even when the cold iron source was used in a large amount of 100 ~ 250 kg / t by total weight of cast iron and the cold iron source (t), the decrease in productivity or the increase in the cost of refining is not triggered and the dissolution of the cold iron source and the preliminary refining of the cast iron can be conducted effectively. However, when the basic unit of the cold iron source exceeds 250 kg / t, there is a problem that another heat source is needed to cause approximately the cost increase or the inflation time is prolonged to decrease productivity. In addition, the additional increase in the amount of use is not effective in view of the restriction of the installation of the loading of the cold iron source.

[0090] Furthermore, as mentioned later in detail, it is preferable to cause an appropriate foaming of the slag inside the converter type refining furnace 1 to improve the slag removal property of a slag 10 after desilication. For this purpose, it is effective to improve the rate of CO gas generated by the reaction between the carbon in the cast iron and the iron oxide in the slag. In order to stably obtain the proportion of slag removal in the subsequent step of slag removal, therefore, it is preferable to supply oxygen in an amount that exceeds the stoichiometric amount necessary to oxidize the silicon in the cast iron and in the added silicon source.

[0091] The basic oxygen unit supplied to the molten iron during desilication is preferable to be a sum of the stoichiometric amount required for desilication and not less than 2 Nm ³ / t, desirably not less than 4 Nm ³ / t. In the invention, the concentration of silicon in the molten iron at the end of desilication by oxygen transmission is not more than 0.2% by mass, preferably not more than 0.1% by mass, more preferably not more than 0 , 05% by mass. Thus, the property of

Petition 870180032588, of 04/20/2018, p. 29/70

26/53 slag removal can be maintained well while maintaining the foaming state even in a slag removal after desilication and slag rephosphorization to the cast iron can be suppressed. According to the studies of the inventors, it has been confirmed that the above effects are obtained by insufflation of oxygen for desilication with an oxygen supply rate through insufflation at the top of 1 ~ 2 Nm ³ / min and a low insufflation of gas by the bottom of approximately 0.02 ~ 0.2 Nm ^{3 /} min. [0092] Even when the desilication of the cast iron is carried out while the total volume of the dephosphorized slag in the previous treatment is left in the oven, the lime content in the dephosphorized slag can be used effectively without causing the phosphorization by combining the control of silicon concentration with the control of the slag basicity and the temperature control of the cast iron. In addition, the concentration of phosphoric acid in the slag can be improved by combining the controls of the silicon concentration, the basicity of the slag and the temperature of the cast iron and also keeping the slag dephosphorized in the previous treatment in the oven, where the formation of foam on the slag. Especially, the phosphoric acid in the slag has an effect of reducing the surface tension of the slag and promotes the reaction with the cast iron or the dispersion of fine bubbles, so that it is considered that even when (T. Fe) is an oxide concentration of relatively low iron as a concentration of approximately 10% by mass, foaming on the slag can be maintained to maintain a good slag removal property.

[0093] (3) Next, an intermediate step (C) of slag removal shown in FIG. 2 (C).

[0094] In the method for the preliminary treatment of cast iron according to the invention, the step of removing the slag is placed

Petition 870180032588, of 04/20/2018, p. 30/70

27/53 above the desilication step to carry out an intermediate removal of the discharge slag from the desilicate slag with a low basicity containing a large amount of SiO2 generated in the desilication from the converter type refining furnace 1. The intermediate removal of desilicate slag 10 is effective in decreasing the amount of solvent for the lime based flux used to adjust the slag basicity in the subsequent dephosphorization step. In addition, in the case of the method for the preliminary treatment of cast iron according to the invention in which the desilication of the new cast iron is carried out while maintaining a large amount of the dephosphorized slag generated by the preliminary treatment of the preceding cast iron in the kiln, desilication is carried out in order to avoid the slag rephosphorization to cast iron, so that the concentration of phosphoric acid in the desilicate slag becomes higher than that of the conventional method. When a large amount of desilicate slag is kept in the oven, the amount of phosphoric acid in the slag becomes excessive in the oven in the subsequent dephosphorization step to decrease the dephosphorization effect, so that the removal of the slag is important to prevent this problem.

[0095] In the method for the preliminary treatment of cast iron according to the invention, when the treatments of steps (A) ~ (E) above are carried out repeatedly and continuously, if the slag discharge after desilication is insufficient, process if the storage of phosphoric acid in the oven, so care needs to be taken. For this reason, when the amount of phosphoric acid in the slag becomes too large in the kiln in the dephosphorization step, the efficiency of dephosphorization is decreased by increasing the concentration of phosphoric acid in the slag to increase the phosphorus concentration in the cast iron after treatment. or to

Petition 870180032588, of 04/20/2018, p. 31/70

28/53 increase the amount of solvent for the lime-based flux needed for the dephosphorization reaction.

[0096] In the invention, therefore, it is preferable that the proportion of desiccated slag removal (% by mass) = (% by mass of slag discharged) x 100 / (% by mass of slag in the oven at the end of desilication) at least not less than 40% by mass, desirably not less than 60% by mass. When the proportion of slag removal is less than 40% by mass, the amount of solvent for the lime based flux used in the subsequent dephosphorization step is increased as mentioned above. In addition, when the amount of slag is increased, the formation of foam in the slag cannot be suppressed and, therefore, the explosion of the slag is caused by the orifice of the furnace during dephosphorization and disturbances of the operation can be caused due to an explosion of the slag. slag.

[0097] In the method for the preliminary treatment of the cast iron according to the invention, the basicity of the slag after desilication is obtained in a range of 0.5 ~ 1.5 and the temperature of the cast iron at the end of desilication is obtained up to not less than 1240 ° C but not more than 1400 ° C and also the basic oxygen unit is appropriately adjusted to promote the formation of foam in the slag, with good slag fluidity and gas delay and good slag removal can be conducted only by tilting the furnace body after desilicating to drain the slag out of the furnace orifice. When the slag has drained out by adjusting the angle of inclination of the furnace body so as not to expel the cast iron, it is necessary to retain a certain amount of slag in the furnace, however the amount of slag retained in the furnace can be controlled to be small because the volume ratio of the slag foam is approximately 1/10 and the graviPetition 870180032588, of 04/20/2018, p. 32/70

29/53 apparent specificity decreases compared to true specific gravity. In addition, when the slag foaming is calmed, the proportion of slag removal is reduced, so that a time from the end of desilication to the beginning of the inclination of the furnace body for slag removal is preferable. that is within 4 minutes.

[0098] When the basicity of the desilicate slag required in the slag removal stage is less than 0.5, as shown in FIG. 3, the slag viscosity is increased and the good proportion of slag removal cannot be guaranteed. Meanwhile, when the basicity of the desilicate slag exceeds 1.5, the slag in the solid phase is generated to decrease the slag's fluidity and decrease the slag removal ratio. From a point of view of guaranteeing the slag removal property and the slag removal ratio, the basicity of the slag is sufficient to be approximately 0.5 ~ 1.5. From the point of view of avoiding slag refosphorization in the desilication step and decreasing the amount of solvent for the used lime based flux, it is more preferable to adjust the slag basicity to a range of 0.8 ~ 1.2 .

[0099] Furthermore, the formation of foam in the slag is promoted by fine bubbles of CO generated by (T. Fe) in the desilicate slag in a step of slag removal, that is, by the reaction of iron oxide and cast iron or granular iron containing carbon suspended in the slag. As the alternative confirmation is conducted to test the appropriate concentration range (T. Fe), in the case of (T. Fe) <5% by mass, the slag's defoaming is insufficient and the driving force is small when the slag is discharged inclination of the converter and sufficient discharge is difficult. On the other hand, in the case of (T. Fe)> 25% by mass, the generation of CO bubbles in a flowing slag is dramatically processed and the phenomenon of

Petition 870180032588, of 04/20/2018, p. 33/70

30/53 shock and therefore is obliged to interrupt the slag removal operation. For this purpose, the appropriate range of (T. Fe) in the slag at the end of desilication or in a slag removal step is (T. Fe) = 5 ~ 25% by weight.

[00100] When the temperature of the desilicate slag is low (less than 1260 ° C) in the treatment in a slag removal step, the slag fluidity is decreased by the increase in slag viscosity associated with the generation of slag in solid phase and by increasing the slag viscosity in the liquid phase to thereby approximately cause a decrease in the proportion of slag removal. Therefore, the basic unit of the cold iron source is adjusted and also at least an amount of heat source addition such as silicon carbide, ferrosilicon or similar and the basic oxygen unit is adjusted depending on the initial conditions of the cast iron used, the temperature of the cast iron at the end of the desilication is obtained up to not less than 1260 ° C and the temperature of the slag is obtained up to not less than 1260 ° C.

[00101] When almost all the slag generated after desilication is removed, the slag formation of the solvent for the freshly added lime based flux in the subsequent dephosphorization step is delayed, which is an obstruction factor of dephosphorization. For this purpose, fluorite can be added to promote slag formation. In this case, however, the use of the slag is subject to restriction as previously mentioned, which obstructs the use of the slag. In addition, there is a process to promote the formation of slag by adding iron oxide such as iron ore or similar. However, this method is not advisable because the heat loss is large due to the endothermic reaction of iron oxide decomposition and the amount of heat that can be used to dissolve the cold iron source is decreased.

Petition 870180032588, of 04/20/2018, p. 34/70

31/53 [00102] Therefore, in order to promote the formation of solvent slag for the lime-based flux without using fluorite or iron oxide in the dephosphorization stage, it is also effective to retain an appropriate amount of the desilicate slag that has the composition preferable and oven temperature and use silicon dioxide or iron oxide in the slag to promote slag formation. In the discharge of desilicate slag, it is preferable that the inclination angle of the furnace body is adjusted while maintaining the preferred slag removal ratio of the desilicate slag to not less than 40%, preferably not less than 60% so to retain 4 ~ 20 kg / t of desiccated slag in the oven. In this way, the dephosphorization reaction can be efficiently promoted without using iron oxide in the dephosphorization stage and it is possible to indirectly use the amount of heat based on the endothermic reaction of iron oxide decomposition as the heat for the dissolution of the source of cold iron in desilication. When the amount of desilicated slag retention is less than 4 kg / t, it is necessary to use iron oxide to promote the formation of slag from the solvent to the lime-based flux in the subsequent dephosphorization step. While exceeding 20 kg / t, there is a problem that the amount of solvent for the used lime based flux is increased, the dephosphorization operation is blocked.

[00103] (4) The dephosphorization step (D) shown in FIG. 2 (D).

[00104] After the slag removal step (C), the dephosphorization of the cast iron is carried out by adding the solvent for the lime based flux to the cast iron retained in the same converter type refining furnace 1 and the insufflation of oxygen as a source of oxygen. As the oxygen source used in this dephosphorization step, it is preferable to use only gaseous oxygen 12 for an insufflation lance 2 Petition 870180032588, of 04/20/2018, p. 35/70

32/53 tion at the top in order to reduce heat loss. Phosphorus in cast iron is oxidized by oxygen in the oxygen source supplied to form phosphorus oxide (P2O5) and phosphorous oxide is stably incorporated and to the slag produced by a slag formation from the solvent to the lime-based flux to promote dephosphorization of cast iron. To efficiently promote the dephosphorization reaction, it is preferable that the dephosphorization is carried out by adding the solvent to the lime-based flux in order to make the basicity of the dephosphorized slag (slag 18 after dephosphorization of the last load) not less than 1 , 2, but not exceeding 3.0 and providing oxygen in order to make the temperature of the cast iron after the end of dephosphorization not less than 1280 ° C, but not more than 1360 ° C.

[00105] When the basicity of the dephosphorized slag 17 generated in this dephosphorization is less than 1.2 or the temperature of the cast iron exceeds 1360 ° C, the slag's dephosphorization capacity is impaired and the phosphorus concentration in the cast iron afterwards treatment may not be diminished sufficiently. Although, when the slag basicity exceeds 3.0, the formation of slag from the solvent to the lime-based flux is difficult and the cost of the solvent to the lime-based flux increases. When the temperature of the cast iron is less than 1280 ° C, slag formation is also difficult and the amount of heat in the subsequent decarburization step is lacking. To sufficiently guarantee the amount of heat in the decarburization step, it is desirable that the temperature of the cast iron after dephosphorization is obtained to not less than 1280 ° C, but not more than 1360 ° C and also the amount of oxygen used and / or the amount of carbon added in the desilicate and dephosphorization is / is adjusted (s) so as to make the concentration of carbon in the cast iron after dephosphorization not

Petition 870180032588, of 04/20/2018, p. 36/70

33/53 less than 2.8% by weight.

[00106] In the operation of the method according to the invention, a case occurs in which the Si concentration, the P concentration and the temperature of the cast iron are varied to make the temperature of the cast iron low after desilication or a case in that the concentration of P in the cast iron is high and the dephosphorization load is high. In this case, to promote lime dissolution in the dephosphorization step, it is effective to inflate a source of lime such as powdered lime, calcium carbonate or similar over the surface of the cast iron by an insufflation lance at the top with gaseous oxygen or gas inert. In a zone of the surface of the cast iron exposed to the insufflation of oxygen from the top, a direct decarburization reaction or an oxidation of the iron is caused to obtain a temperature above approximately 2000 ° C and, therefore, fusion is promoted by the addition of powdered lime. to such an area.

[00107] In the method for the preliminary treatment of the cast iron according to the invention, the slag containing SiO2 that contributes to the melting of the lime is discharged after desilication, so that the premature dissolution is effective by loading the powdered lime . In this method, the heat of oxidation of Si in the cast iron is used to promote the dissolution of the cold iron source. Therefore, operation at a higher temperature is preferable in relation to the rate of dissolution of the scrap in the cast iron. However, the higher the temperature, the more inconvenient it is to refosphorize, desilicate and dephosphorize. In the invention, therefore, insufflation from the top of the pulverized iron oxide is carried out simultaneously in the zone exposed to oxygen insufflation from the top and only the reaction zone is cooled locally by the iron oxide decomposition reaction (endothermic reaction), in which it becomes possible to try to dephosphorize or suppress phosphorization under conditions of

Petition 870180032588, of 04/20/2018, p. 37/70

34/53 macroscopically higher temperature. As the auxiliary material containing lime or calcium carbonate may not only be a single substance, but also recycled materials such as the slag generated in insufflation with decarburization in converter and the like. In addition, as iron oxide can be used not only as a single substance of iron ore or similar, but also recycled materials such as rolling scales, sintered powdered ore, collected fine powder and the like.

[00108] (5) Next, a spill step (E) shown in FIG. 2 (E).

[00109] In this step (E), the cast iron in the converter-type refining furnace is poured into a container containing the cast iron (which does not appear in the figure) by tilting the converter-type refining furnace 1 to one end equipped of a discharge orifice when the phosphorus concentration in the cast iron through the dephosphorization step above is decreased to a given value. In addition, it is preferable that the given value of the phosphorus concentration is not greater than 0.030% by mass.

[00110] As mentioned before, the method for the preliminary treatment of the cast iron according to the invention is a continuous treatment of pouring of the cast iron after dephosphorization, leaving at least part of the slag dephosphorized in the oven without being discharged and carrying iron. new cast to conduct desilication. Therefore, most of the slag discharged from the converter-type refining furnace (furnace for preliminary treatment) is a slag after desilication, which can decrease the incorporation of dephosphorized slag which has a relatively high basicity. This avoids a case in which if dephosphorized slag is incorporated, there is a feared elution with alkali or swelling due to the hydration reaction to restrict the use of the slag. EspeciallyPetition 870180032588, of 04/20/2018, p. 38/70

35/53 te, such a problem not completely caused in a process that does not discharge the dephosphorized slag, so that the slag treatment can be simplified and it is possible to use the slag for additional high-value applications. In particular, this has a great effect in a case where the preliminary treatment of the cast iron is carried out continuously and repeatedly with a converter as in the invention.

EXAMPLES [00111] The preliminary treatment of the cast iron according to the invention is carried out with a 250 ton capacity converter type refining oven 1 as shown in FIG. 1. In this treatment, the gaseous oxygen is insufflated by means of a lance 2 for insufflation from the top towards a bath surface (cast iron), while the gaseous nitrogen for stirring is insufflated to the cast iron through five insufflation nozzles. at the bottom arranged at the bottom of the oven body. In all the Examples presented in Table 1 and a part of the Comparative Examples presented in Table 2, part or all of the dephosphorized slag produced by dephosphorization of the preceding cast iron is retained in the furnace for refining of the converter type and a cold iron source is first charged at the same time and then the cast iron is loaded into the furnace and after that oxygen is inflated from the top to start desilication. In one part of the operation, SiC briquettes and non-oxide Si are used as a silicon source for a heat source in desilication and quicklime is used as a solvent for the lime based flux for the basicity adjustment. and added to the oven on top. After desiccation is complete, the furnace body is immediately tilted to conduct the slag removal. Subsequently, quicklime and gaseous oxygen are supplied and iron ore is added in part of the operation to conduct dephosphorization. a

Petition 870180032588, of 04/20/2018, p. 39/70

36/53 period of time from the beginning of desilication to the end of emptying after dephosphorization is approximately 30 minutes.

[00112] As the cold iron source is used iron scrap defined in Uniform standards of Ferrous Scraps of the Japan ferrous raw materials association (The Japan ferrous raw materials association). [00113] The operating conditions and the results of the operation are presented in Table 1 in relation to the Examples of the Invention and in Table 2 in relation to the Comparative Examples, respectively. In any operation, iron oxide is not used in desilication, but the basicity of the slag discharged from the kiln for refining the converter type in a step of slag removal after desilication is obtained up to a target value except for Comparative Example 3, so that the slag is formed sufficiently.

Petition 870180032588, of 04/20/2018, p. 40/70

Table 1

Item unity Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Slag dephosphor- rized prayer- tooth CaO / SiO2 Mass Ratio 1.5 1.2 1.8 1.8 1.5 1.8 1.5 1.6 2.1 Retention Ratio % in pasta 100 100 33 63 100 100 100 100 100 Retained quantity kg / t 25 28 8 15 25 24 25 24 24 Load- gamento Quantity of cast iron kg / t 875 840 880 880 896 916 850 820 900 Cast iron temperature ° C 1280 1275 1290 1283 1295 1296 1278 1263 1284 [C] on cast iron % in pasta 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 [Si] in cast iron % in pasta 0.39 0.42 0.36 0.37 0.44 0.45 0.42 0.86 0.26 [P] in cast iron % in pasta 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 Scrap quantity kg / t 125 160 120 120 104 84 150 180 100

37/53

Petition 870180032588, of 04/20/2018, p. 41/70

Item unity Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Desilica- tization Briquettes from SiC kg / t 0 3.6 0 0 0 0 3.6 0 0 Si without oxide kg / t 3.4 5.1 3.2 3.3 4.0 4.1 5.1 7.1 2.4 Live Lime kg / t 0 0 1.2 0 0 0 0 0 0 Basic oxygen unit Nm ³ / t 8.0 10.0 8.0 8.0 8.0 8.0 10.0 12.0 7.0 Temperature at the end ° C 1271 1273 1281 1277 1320 1346 1290 1292 1270 C at the end % in pasta 3.5 3.4 3.5 3.5 3.7 3.8 3.4 3.3 3.6 Si at the end % in pasta 0.01 0.02 0.01 0.01 0.01 0.02 0.02 0.10 0.01 P at the end % in pasta 0.09 0.11 0.11 0.10 0.10 0.11 0.10 0.11 0.08 CaO / SiO2 at the end Bulk proportion 0.70 0.53 0.52 0.60 0.65 0.72 0.57 0.50 1.07 Slag quantity at the end kg / t 34 41 19 24 35 34 38 41 29 Intermediate slag removal Discharge ratio % in pasta 56 63 47 58 72 65 79 63 59 Retained quantity kg / t 15.0 15.0 10.0 10.0 10.0 12.0 8.0 15.0 12.0

38/53

Petition 870180032588, of 04/20/2018, p. 42/70

Item unity Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Phosphorus rization Lime live on kg / t 5.4 6.3 6.1 6.5 7.0 6.5 7.7 7.5 5.0 Basic oxygen unit Nm ³ / t 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Iron ore kg / t 0.0 0.0 0.0 0.0 5.0 8.0 0.0 4.0 0.0 Temperature at the end ° C 1332 1335 1339 1335 1359 1380 1349 1354 1332 C at the end % in pasta 3.0 2.9 3.0 3.0 3.0 3.1 2.9 2.8 3.1 P at the end % in pasta 0.020 0.027 0.027 0.022 0.022 0.021 0.018 0.028 0.019 CaO / SiO2 at the end % in pasta 1.5 1.2 1.2 1.4 1.5 1.8 1.5 1.2 1.5 Amount of dephosphorized slag kg / t 25 30 24 24 25 24 25 31 24 Y - 250 240 252 251 260 266 243 244 253 Lime in total kg / t 5.4 6.3 7.3 6.5 7.0 6.5 7.7 7.5 5.0

39/53

Petition 870180032588, of 04/20/2018, p. 43/70

Table 2

Item unity Example Comparative 1 Example Comparative 2 Example Comparative 3 Example Comparative 4 Example Comparative 5 Slag dephosphor- rized prayer- tooth CaO / SiO2 Bulk proportion 1.5 1.1 1.1 1.2 1.2 Retention ratio % in pasta 0 50 65 70 62 Retained quantity kg / t 0 34 26 28 30 Load- gamento Quantity of cast iron kg / t 925 850 895 910 875 Cast iron temperature ° C 1280 1280 1280 1320 1280 [C] cast iron % in pasta 4.6 4.6 4.6 4.6 4.6 [Si] in cast iron % in pasta 0.40 0.40 0.40 0.50 0.40 [P] cast iron % in pasta 0.12 0.12 0.12 0.12 0.12 Scrap quantity kg / t 75 150 105 90 125

40/53

Petition 870180032588, of 04/20/2018, p. 44/70

Item unity Example Comparative 1 Example Comparative 2 Example Comparative 3 Example Comparative 4 Example Comparative 5 Desilica- tization briquettes from SiC kg / t 3.6 3.6 3.6 0 3.6 Si without oxide kg / t 5.2 4.9 5.1 4.6 5.0 Live Lime kg / t 8.0 0 0 0 0 Basic oxygen unit Nm ³ / t 7.5 10.0 10.0 9.0 7.0 Temperature at the end ° C 1348 1290 1350 1405 1265 C at the end % in pasta 3.9 3.5 3.6 3.7 3.7 Si at the end % in pasta 0.15 0.02 0.01 0.01 0.13 P at the end % in pasta 0.11 0.11 0.14 0.13 0.12 CaO / SiO2 at the end Bulk proportion 1.0 0.55 0.47 0.55 0.62 Slag quantity at the end kg / t 23 49 40 40 40 Intermediate slag removal Discharge ratio % in pasta 100 0 62 62 32 Retained quantity kg / t 0 49 15 15 27

SS / H7

Petition 870180032588, of 04/20/2018, p. 45/70

Item unity Example Comparative 1 Example Comparative 2 Example Comparative 3 Example Comparative 4 Example Comparative 5 Phosphorus rization Live Lime kg / t 9 11.6 10.3 10.5 9.8 Basic oxygen unit Nm ³ / t 6.0 6.0 6.0 6.0 7.0 Iron ore kg / t 15.0 0.0 12.0 12.0 0.0 Temperature at the end ° C 1350 1356 1357 1391 1358 C at the end % in pasta 3.2 2.9 2.9 2.9 3.1 P at the end % in pasta 0.020 0.030 0.030 0.031 0.029 CaO / SiO2 at the end % in pasta 1.5 1.1 1.1 1.2 1.2 Amount of dephosphorized slag kg / t 23 68 40 40 48 Y - 264 243 256 271 250 Total quicklime kg / t 17.0 11.6 10.3 10.5 9.8

42/53

Petition 870180032588, of 04/20/2018, p. 46/70

43/53 [00114] Examples 1, 2 and 5 ~ 9 are a case where the preliminary treatment of the next cast iron is carried out while a total amount of dephosphorized slag after dephosphorization of the previous cast iron is retained in the oven and the Example Comparative 1 is a case in which a total amount of slag is discharged after dephosphorization of the preceding cast iron for comparison. In addition, Comparative Example 2 is a case where dephosphorization is carried out continuously without discharging the desilicate slag after desilicate.

[00115] In Examples 1 ~ 9 adapted to a method of the invention, conditions such as basicity and amount of retention in the oven (retention ratio and discharge ratio) of dephosphorized slag and desilicate slag, the temperature after desilicate, the concentration of silicon in cast iron etc. are changed variably. Under any conditions, the concentration of phosphorus in the cast iron after dephosphorization is as low as less than approximately 0.03% by weight at a small amount of approximately 5 ~ 7.7 kg / t used lime and an amount of scrap is large compared to Comparative Example 1. In contrast, Comparative Example 1 discharges all amounts of slag after dephosphorization of the preceding cast iron and desilicate slag, so that the phosphorus concentration in the cast iron after treatment is low, but the amount of quicklime used is increased and a large amount of iron ore is necessary for the formation of slag during dephosphorization and, therefore, the amount of scrap used is small.

[00116] In Comparative Example 2, dephosphorization is carried out without discharging the slag after desilication, so that the amount of slag after dephosphorization is increased significantly and the amount of quicklime used is also increased.

Petition 870180032588, of 04/20/2018, p. 47/70

44/53

In Comparative Example 3, the slag basicity after desilication decreases to less than 0.5, which is considered to cause approximately refosphorization and also the amount of quicklime used becomes greater for the adjustment of the basicity in dephosphorization. In Comparative Example 4, the temperature after desilication becomes higher than 1380 ° C, which is considered to cause approximately phosphorization and also the amount of quicklime used becomes higher for adjusting the basicity in dephosphorization. In Comparative Example 5, desilication is terminated as long as the desilication reaction is not processed sufficiently, so that the slag's foaming is easily calmed and the proportion of the desilicated slag discharge becomes weak and the amount of quicklime used becomes greater.

[00117] To make the difference in treatment conditions evident in the slag removal property, slag removal is not carried out after desilication and a removal test is carried out by tilting the oven after desilication + dephosphorization. Considering the Si concentration in the cast iron, the basicity (Ca / SiO2) is adjusted up to 1.5 after desilication + dephosphorization and as a result, (T. Fe) is 10 ~ 30% by mass, [Si] after treatment is Tr., [P] is 0.050 ~ 0.070% by weight and the temperature of the cast iron is 1340 ~ 1360 ° C. The slag foaming is not substantially caused and the slag that has a high proportion and solid phase is discharged and it is difficult to control the amount of discharge by tilting the furnace. That is, the behavior of the slag and the foaming condition are different in the discharge of the slag after desilicate and after desilicate + dephosphorization, so that the appropriate conditions of the slag composition cannot be applied.

[00118] For the comparison between Example 1 and Example CompaPetição 870180032588, of 04/20/2018, p. 48/70

45/53 rative 4, it can be seen that dephosphorization can be conducted efficiently by increasing the amount of scrap used and decreasing the temperature after desilication to decrease the amount of quicklime used while suppressing slag rephosphorization.

[00119] The influence of basicity during desilication is examined in the same way as the test in Tables 1 and 2. The results are shown in Table 3. As noted by Table 3, in Examples 11 and 12 that satisfy basicity during desilication 0.8 ~ 1.5, refosphorization is not caused and the phosphorus concentration after dephosphorization is good. In contrast, in Example 10 where the basicity during desilication is outside 0.8 ~ 1.5, the phosphorization is caused and the phosphorus concentration after dephosphorization becomes somewhat high.

Petition 870180032588, of 04/20/2018, p. 49/70

Table 3

Item unity Example 10 Example 11 Example 12 Dephosphorized slag pre- assignor CaO / SiO2 Bulk proportion 1.6 1.8 1.9 Retention ratio % in large scale 100 100 100 Retained quantity kg / t 30 33 28 Carries- ment Quantity of cast iron kg / t 877 879 875 Cast iron temperature ° C 1250 1,239 1,286 [C] cast iron % in large scale 4.51 4.46 4.59 [Si] in cast iron % in large scale 0.55 0.46 0.45 [P] cast iron % in large scale 0.120 0.122 0.121 Scrap quantity kg / t 123 121 125

46/53

Petition 870180032588, of 04/20/2018, p. 50/70

Item unity Example 10 Example 11 Example 12 Desilicate zation Briquettes from SiC kg / t 0.0 0.0 0.0 Si without oxide kg / t 0.0 0.0 0.0 Live Lime kg / t 1.0 1.6 1.1 Basic oxygen unit Nm ³ / t 7.8 8.0 7.9 Lower CaO / SiO2 limit during insufflation Bulk proportion 0.68 0.82 0.85 Upper limit of CaO / SiO2 during insufflation Bulk proportion 1.00 1.18 1.45 Temperature at the end ° C 1300 1275 1305 C at the end % in large scale 3.85 3.78 3.87 Si at the end % in large scale 0.04 0.01 0.02 P at the end % in large scale 0.145 0.105 0.100 CaO / SiO2 at the end Bulk proportion 0.70 0.82 0.90 (% T.Fe) at the end % in large scale 12.3 16.4 17.8 Slag quantity at the end kg / t 44.3 48.8 51.9 Intermediate slag removal Discharge ratio % in large scale 58 60 65 Retained quantity kg / t 19 20 18

47/53

Petition 870180032588, of 04/20/2018, p. 51/70

Item unity Example 10 Example 11 Example 12 Dephosphoris zation Quick lime (top addition) kg / t 0.0 0.0 0.0 Live lime (pitch) kg / t 6.4 6.4 6.3 Calcium carbonate (pitch) kg / t 0.0 0.0 0.0 Iron oxide (pitch) kg / t 0.0 0.0 0.0 Basic oxygen unit Nm ³ / t 7.5 8.0 8.5 Iron ore (top addition) kg / t 0.0 0.0 4.0 Temperature at the end Ό 1383 1,360 1,353 C at the end % in large scale 2.62 2.88 2.99 P at the end % in large scale 0.027 0.020 0.018 CaO / SiO2 at the end Bulk proportion 1.73 2.05 2.11 Amount of dephosphorized slag kg / t 35 32 31 Y - 249 245 252 Total quicklime kg / t 7.4 8.1 7.4

Calculation formula CaOa [lcg / t] + CaOb [kg / t]

SIO _2a [kg / t] + SIO _2b [kg / t]

The calculation formula above is used in the calculation of CaO / SiC> 2 during insufflation for desilication. CaOa: amount of lime dissolution loaded CaOb: CaO in the retained slag

SiO _2a : Si amount burned * 2.14

SiO2t>: retained slag S1O2

48/53

Petition 870180032588, of 04/20/2018, p. 52/70

49/53 [00120] In addition, the influence of T. Fe at the end of desilication in the period of intermediate slag removal is examined as the tests in Tables 1 and 2. The results are presented in Table 4, as observed by Examples 13 ~ 16 in Table 4, a larger amount of scrap can be used in all examples and the amount of quicklime used can be decreased. Particularly, in Examples 13 and 14 which provide powdered quicklime, calcium carbonate and iron oxide through the insufflation lance at the top in the dephosphorization step, increase the slag formation / melting rate of the quicklime and the phosphorus concentration afterwards of the treatment the same amount of quicklime is as low as [P] <0.020% by weight. In the method of Examples 13 and 14 where (T. Fe) in the desilicate slag in a slag removal step is 5 ~ 25% by mass, the intermediate slag removal time can be shortened and the intermediate slag removal property it's good. In contrast, Example 15 has (T. Fe) low in the desilicate slag in the slag removal step and takes a long time to intermediate slag removal compared to Examples 13 and 14, On the other hand, Example 16 has ( T. Fe) high in desilicated slag in a slag removal step and causes shock phenomenon, so it takes time to calm the slag and the slag removal time is increased.

Petition 870180032588, of 04/20/2018, p. 53/70

Table 4

Item unity Example 13 Example 14 Example 15 Example 16 Slag phosphorized precedent CaO / SiO2 Bulk proportion 1.9 1.8 1.2 1.2 Retention ratio % in large scale 100 100 100 100 Retained quantity kg / t 25 24 27 28 Carries- ment Quantity of cast iron kg / t 900 900 900 900 Cast iron temperature ° C 1250 1300 1300 1300 [C] cast iron % in large scale 4.6 4.6 4.6 4.6 [Si] in cast iron % in large scale 0.45 0.45 0.45 0.45 [P] cast iron % in large scale 0.12 0.12 0.12 0.12 Scrap quantity kg / t 100 100 100 100

50/53

Petition 870180032588, of 04/20/2018, p. 54/70

Item unity Example 13 Example 14 Example 15 Example 16 Desilicate zation Briquettes from SiC kg / t 3.6 3.6 3.6 3.6 Si without being oxide kg / t 5.0 5.0 5.0 5.0 Live Lime kg / t 0 0 0 0 Basic oxygen unit Nm ³ / t 7.0 7.0 6.3 12.0 Temperature at the end ° C 1270 1320 1295 1390 C at the end % in large scale 3.9 3.8 3.9 3.4 Si at the end % in large scale 0.05 0.05 0.13 0.01 P at the end % in large scale 0.12 0.12 0.13 0.12 CaO / SiO2 at the end Bulk proportion 1.10 1.20 1.0 1.0 (% T.Fe) at the end % in large scale 15 14 3 28 Slag quantity at the end kg / t 30 30 30 35 Intermediate slag removal Discharge ratio % in large scale 75 77 76 72 Retained quantity kg / t 7.5 6.9 7.2 9 Slag removal time minutes 6.0 6.0 10 15

51/53

Petition 870180032588, of 04/20/2018, p. 55/70

Item unity Example 13 Example 14 Example 15 Example 16 Quick lime (top addition) kg / t 0 0 8.0 6.5 Live lime (pitch) kg / t 4 4 0 0 Calcium carbonate (pitch) kg / t 6 6 0 0 Iron oxide (pitch) kg / t 0 5 0 0 Basic oxygen unit Nm ³ / t 6 6 7.7 3.0 Dephosphoris Iron ore (addition by kg / t 5 5 0 0 zation top) Temperature at the end ° C 1330 1360 1390 1385 C at the end % in large scale 3.3 3.2 3.1 3.1 P at the end % in large scale 0.012 0.013 0.038 0.033 CaO / SiO2 at the end % in large scale 1.5 1.7 1.6 1.5 Amount of dephosphorized slag kg / t 25 25 26 25 Y - 253 262 262 262 Total quicklime kg / t 7.0 7.0 8.0 6.5

52/53

Petition 870180032588, of 04/20/2018, p. 56/70

53/53

INDUSTRIAL APPLICABILITY [00121] The preliminary treatment of the cast iron according to the invention can effectively decrease the phosphorus concentration while suppressing the amount of used flux and the amount of slag generated and can lead to the dissolution of the cold iron source such as scrap iron. iron, cold cast iron or similar effectively. This technique can be applied to treatment not only with the converter type refining furnace but also the other refining converter that has a similar construction.

DESCRIPTION OF REFERENCE SYMBOLS converter-type refining furnace for insufflating from the top ventral to insufflating from the bottom dump holes deposits

6, 8 chutes cast iron slag deposit after desilication the cold iron source gaseous oxygen insufflation gas through the bottom loading shell solvent silicon source for the slag based flux after dephosphorization

Petition 870180032588, of 04/20/2018, p. 57/70

1/4

Claims (12)

1. Process for the preliminary treatment of cast iron by conducting cast iron desilication and dephosphorization with a converter-type container in which the cast iron poured from a blast furnace is first loaded into the converter-type container to conduct the desilicate and then the cast iron and a portion of the slag after desilication are retained in the container to conduct intermediate slag removal and subsequently the cast iron and the slag retained in the container after desilication are added with a solvent-based flux while there is insufflation of oxygen to conduct dephosphorization of the cast iron, characterized by the fact that no less than 30% by weight of the slag that has the slag basicity not less than 1.2 after dephosphorization are retained in the converter-type container and then by minus the untreated cast iron is loaded into the container containing the slag after dephosphor ization to conduct desilication and the concentration of silicon in the molten iron at the end of desilication is obtained up to not more than 0.2% by mass and the basicity of the slag after desilication is obtained up to not less than 0.5 but not more than 1.5 and the temperature of the cast iron is made not less than 1240 ° C but not higher than 1400 ° C and thereafter an intermediate removal of the discharge slag not less than 40% by weight of the slag after desilicating the container it is conducted and subsequently dephosphorization is conducted in the same container. 2. Process for the preliminary treatment of cast iron according to claim 1, characterized by the fact that the basicity of the slag after dephosphorization is not greater than 3.0. 3. Process for the preliminary treatment of cast iron according to claim 1 or 2, characterized by the fact that the Petition 870180032588, of 04/20/2018, p. 58/70 2/4 slag after dephosphorization is retained in the container to not less than 60% by mass of an amount generated by dephosphorization. 4. Process for the preliminary treatment of cast iron according to any one of claims 1 to 3, characterized by the fact that the basicity of the slag during desilication is not less than 0.8, but not greater than 1.5 . 5. Process for the preliminary treatment of cast iron according to any one of claims 1 to 4, characterized by the fact that the slag after desilication has a slag basicity of not less than 0.8 but not greater than 1, 5 and T. Fe not less than 5% by weight but not more than 25% by weight. Process for the preliminary treatment of cast iron according to any one of claims 1 to 5, characterized by the fact that the cold iron source is loaded during desilication. Process for the preliminary treatment of cast iron according to any one of claims 1 to 6, characterized in that the desilication is carried out by loading the cold iron source into the converter-type container in addition to the cast iron poured from the top furnace and oxygen insufflation to bring the temperature of the cast iron at the end of desilication to not less than 1260 ° C, but not more than 1350 ° C. 8. Process for the preliminary treatment of cast iron according to any one of claims 1 to 7, characterized in that an amount of the cold iron source that satisfies the following equation is loaded into the desilicate by a total amount of cast iron loaded in the converter-type container and the cold iron source: Petition 870180032588, of 04/20/2018, p. 59/70 3/4 Y = (3 + 34.5 [% Si] + 0.21Ti) · (1000- Xs) / 1000 where Y is 230 ~ 270, [% Si] is the concentration of silicon in the loaded cast iron (% by mass) ), Ti is the temperature of the loaded cast iron (° C) and Xs is a basic unit of the cold iron source (kg / t). Process for the preliminary treatment of cast iron according to any one of claims 1 to 8, characterized by the fact that the concentration of cast iron silicon at the end of the desilication is not more than 0.1% by mass. 10. Process for the preliminary treatment of cast iron according to any one of claims 1 to 9, characterized in that the desilication is carried out by loading or adding 100 ~ 250 kg / t of a cold iron source by total weight of cast iron and cold iron source and 2 ~ 10 kg / t of iron silicate, metallic silicon, silicon carbide or silicon nitride as oxidizable silicon for the converter type container. 11. Process for the preliminary treatment of cast iron according to any one of claims 1 to 10, characterized by the fact that dephosphorization is carried out by retaining 4 ~ 20 kg / t of the slag after desilicate by total weight of the source cold iron and cast iron in the converter-type container after intermediate slag removal, addition of a lime based flux solvent and oxygen insufflation to make the slag basic after dephosphorization to not less than 1.2 but not more than 3.0 and the temperature of the cast iron after the end of dephosphorization to not less than 1280 ° C but not more than 1360 ° C. 12. Process for the preliminary treatment of cast iron according to any one of claims 1 to 11, characterized in that the dephosphorization is conducted by jet of a refining agent containing at least one powdered lime ingredient, specification 870180032588 , of 04/20/2018, p. 60/70 4/4 calcium bonate and iron oxide to cast iron by means of an insufflation lance at the top. Petition 870180032588, of 04/20/2018, p. 61/70 1/4